UDP based DNS server/filter - Feature Request

[sumukhs]

Similar to previously closed issue.

This feature request is to run Envoy as a DNS server. A new filter section for DNS can be added, which contains mapping from the dns name to the cluster name. The mapping can be configured statically via the config file or dynamically using xDS API.

Motivation:
We currently have a separate DNS server handling dns requests for our services and with the move to Envoy as our primary routing layer for service-service communication, we would like to move the dns handling as well to a centralized component that is already aware of how to route requests.

Since the filter framework works on a given listener, a UDP filter stack is required for this to work. I see some WIP for a UDP proxy. Would its completion enable this scenario more seamlessly?

@mattklein123

[mattklein123]

Since the filter framework works on a given listener, a UDP filter stack is required for this to work. I see some WIP for a UDP proxy. Would its completion enable this scenario more seamlessly?

Yes, we would need to complete UDP basic filter support for this to be implemented as an extension. cc @envoyproxy/quic-dev

[sumukhs]

Thanks @mattklein123 .

Is there an existing PR or work stream where we can contribute?
@appario and myself would be available to work on this effort.

[cmluciano]

@sumukhs I am currently working on plumbing UDP into upstream paths. I can cc on this PR once pushed (fixing some tests this week).

[sumukhs]

Thanks @cmluciano. Could you share the private repo/PR link? Is there a target date you are aiming for?

[sumukhs]

cc-ing others who have been involved in this area - @conqerAtapple @alyssawilk

I am trying to get up to speed on the history of how the UDP stack has been shaping up... I found design docs (including QUIC) and active work on the QUIC area these days.

I also see some closed PR's by @conqerAtapple in favor of smaller work items and I have seen the UDP listener is checked in now.

Is @cmluciano the only person actively working on the UDP stack outside of QUIC? I would like to get involved (with another co-worker at Microsoft) in the UDP effort to build the required pieces to shape up the filter stack so that we are able to write a DNS filter.

Can someone comment on what the road map is and give us more context. Happy to join the community call tomorrow morning (5/6) to talk more.

[mattklein123]

@sumukhs I would probably assume at this point that no one is working on basic UDP filters. I would love to see this happen. Maybe it would be easiest to setup a small meeting and we can discuss? Please email me at mattklein123@gmail.com to schedule. Thank you.

[sumukhs]

@mattklein123 - this is an initial draft of the proposed changes for supporting DNS type of filters.

https://docs.google.com/document/d/1uMGhZ4oizCE3nbmGtes20yb-m9cvWvMLfzanZXc81xM/edit?usp=sharing

[mattklein123]

@sumukhs looks like on the right track. I dropped some comments in. Very exciting stuff. cc @envoyproxy/quic-dev @envoyproxy/maintainers if anyone else wants to take a look at the doc. Thank you!